Gate-Tunable Giant Negative Magnetoresistance in Tellurene Driven by Quantum Geometry

Negative magnetoresistance in conventional two-dimensional electron gases is a well-known phenomenon, but its origin in complex and topological materials, especially those endowed with quantum geometry, remains largely elusive. Here, we report the discovery of a giant negative magnetoresistance, reaching a remarkable - 90\% of the resistance at zero magnetic field, R₀, in n-type tellurene films. This record-breaking effect persists over a wide magnetic field range (measured up to 35 T) at cryogenic temperatures and is suppressed when the chemical potential shifts away from the Weyl node in the conduction band, strongly suggesting a quantum geometric origin. We propose two novel mechanisms for this phenomenon: a quantum geometric enhancement of diffusion and a magnetoelectric spin interaction that locks the spin of a Weyl fermion, in cyclotron motion under crossed electric boldsymbol{cal E} and magnetic {bf B} fields, to its guiding-center drift, \(boldsymbol{cal E}times{bf B}\)cdotσ. We show that the time integral of the velocity auto-correlations promoted by the quantum metric between the spin-split conduction bands enhance diffusion, thereby reducing the resistance. This mechanism is experimentally confirmed by its unique magnetoelectric dependence, ΔR_zz\(boldsymbol{cal E},{bf B}\)/R₀=-β_g\(boldsymbol{cal E}times{bf B}\)², with β_g determined by the quantum metric. Our findings establish a new, quantum geometric and non-Markovian memory effect in magnetotransport, paving the way for controlling electronic transport in complex and topological matter.